DESCRIPTION (Applicant's Description) Limited information is available on the association of dietary fat with non-melanoma skin cancer(NMSC) in humans. This investigation, which will comprise the primary component of a doctoral dissertation, is an efficient approach to examine the association of dietary fat and risk of NMSC using information collected during a completed skin cancer prevention trial. NMSC has an incidence rate higher than that of all other types of cancer combined. While older individuals are at higher risk for NMSC, increases in incidence over the past 25 vears are greater than can be accounted for by aging of the U.S. population alone. Ultraviolet radiation (UVR) from sunlight is considered the primary causal agent of NMSC. Dietary fat is associated with three of the mechanisms by which UVR leads to skin carcinogenesis: immunity, inflammatory response, and the integrity of cellular membranes. Animal studies and a recent clinical trial support the link between higher levels of dietary fat and increased incidence of skin cancer. This investigation will develop a cohort population of men and women greater than 3O years of age (sample size of 1016) from the control arm of a recently completed Arizona Cancer Center 5-year skin cancer prevention trial. Information from baseline food frequency questionnaires (FFQs) will be used to develop exposure groupings for fat, linoleic acid, and percent of calories from fat. The risk of occurrence of histologically confirmed endpoints, (all NMSC, basal cell carcinoma (BCC), and squamous cell carcinoma (SCC)) will be evaluated by exposure level. The two primary hypotheses are (1) lower level of usual grams of fat consumed daily is independently associated with decreased incidence of NMSC over 5 years of follow-up among a high risk population, and (2) higher levels of dietary polyunsaturated fatty acid, specifically linoleic acid, is independently associated with increased incidence of NMSC over 5 years of follow-up among a high risk population.